Bp's are pretty amazing creatures and given the right care this rescue could surprise you. I'm with the others here saying to start small with any food items. A regurge is a clear sign her system isn't quite ready for 3 rats just yet but its very promising that she held the last one down. Once she gets a good week of proper temps and holding the meal down I would try feeding her again. Keep the humidity nice and high for her and try to let her adjust to her new surroundings. Good luck with finding a vet in your area that knows how to treat herps. I hope to see pictures in a few months with her fat and healthy.